The present disclosure relates to surface coatings, particularly surface coatings for the front-face or aperture plate of piezoelectric print heads. More specifically, the present disclosure relates to oleophobic surface coatings comprised of polypyrroles containing a fluoroalkyl moiety to be applied to conductive surfaces or metal surfaces, such as the front-face or aperture plate of piezoelectric print heads and image transfix rolls or belts.
Liquid ink jet systems typically include one or more printheads having a plurality of ink jets from which drops of fluid are ejected towards a recording medium. The ink jets of a printhead receive ink from an ink supply chamber or manifold in the printhead, which, in turn, receives ink from a source, such as a melted ink reservoir or an ink cartridge. Each ink jet includes a channel having one end in fluid communication with the ink supply manifold. The other end of the ink channel has an orifice or nozzle for ejecting drops of ink. The nozzles of the ink jets may be formed in an aperture or nozzle plate that has openings corresponding to the nozzles of the ink jets. During operation, drop-ejecting signals activate actuators in the ink jets to expel drops of fluid from the ink jet nozzles onto the recording medium. By selectively activating the actuators of the ink jets to eject drops as the recording medium and/or printhead assembly are moved relative to one another, the deposited drops can be precisely patterned to form particular text and graphic images on the recording medium. An example of a full width array printhead is described in U.S. Patent Publication No. 2009/0046125, which is hereby incorporated by reference herein in its entirety.
In general, inks for ink jet printing may include, for example, aqueous inks and non-aqueous inks. An example of non-aqueous inks includes phase change inks (sometimes referred to as “hot melt inks”), which exist in the solid phase at ambient temperature, but exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the jet operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the recording substrate, either directly or via an intermediate heated transfer belt or drum, they quickly solidify to form a predetermined pattern of solidified ink drops. Phase change inks for color printing typically comprise a phase change organic phase change carrier composition, which is combined with a phase change ink compatible colorant.
Illustrative examples of suitable colorants can include dyes or pigments, as disclosed in, for example, U.S. Pat. No. 5,221,335, the disclosure of which is totally incorporated herein by reference.
U.S. Pat. No. 5,621,022, the disclosure of which is totally incorporated herein by reference, discloses the use of a specific class of polymeric dyes in phase change ink compositions. Further, U.S. Pat. No. 7,699,922, the disclosure of which is totally incorporated herein by reference, discloses organic phase change inks containing nanoparticles.
Suitable inks for inkjet printing can also include ultra-violet curable inks. The examples of ultra-violet curable gel inks, which can be jetted in such a printhead, are described in U.S. Pat. Nos. 7,632,546; 7,625,956; 7,559,639; and 7,553,011; and U.S. Patent Application Publication No. 2007/0123606, each of which are totally incorporated by reference herein in their entireties.
One difficulty faced by fluid ink jet systems is wetting, drooling or flooding of inks onto the printhead front face. Such contamination of the printhead front face can cause or contribute to blocking of the ink jet nozzles and channels, which alone or in combination with the wetted, contaminated front face, can cause or contribute to non-firing or missing drops, undersized or otherwise wrong-sized drops, satellites, or misdirected drops on the recording medium and thus result in degraded print quality.
Conventional printhead front face coatings are typically sputtered polytetrafluoroethylene coatings. When the printhead is tilted, the UV gel ink, at a temperature of about 75° C. (75° C. representing a typical jetting temperature for UV gel ink), and the solid ink, at a temperature of about 105° C. (105° C. representing a typical jetting temperature for solid ink), do not readily slide on the printhead front face surface. Instead, these inks flow along the printhead front face and leave an ink film or residue on the printhead, which can interfere with jetting. For this reason, the front faces of UV and solid ink printheads are prone to becoming contaminated by UV and solid inks, for example. In some cases, the contaminated printhead can be refreshed or cleaned with a maintenance unit. However, such an approach introduces system complexity, additional hardware costs, and can lead to reliability issues.
Thus, there remains a need for materials and methods for preparing devices having oleophobic surface characteristics. Further, while currently available coatings for ink jet printhead front faces are suitable for their intended purposes, a need remains for an improved printhead front face design that reduces or eliminates wetting, drooling, flooding, or contamination of UV or solid ink over the printhead front face. There further remains a need for an improved printhead front face coating that is oleophobic and provides a known surface energy surface near the orifice exit.